Whey or natural proteins: which builds more muscle?

A tub of whey costs as much as several kilos of chicken. The promise: a ‘superior’ protein that is absorbed more quickly and is said to build more muscle than a proper meal. Research backs up whey on one specific point — and contradicts it on almost everything else. Here’s what the studies say that have compared the powder with a proper meal, head-to-head.

Firstly, what protein powder actually does

Let’s start with the most robust figure in this field. A 2018 meta-analysis pooled the results of trials on protein supplementation in healthy adults who were doing resistance training. It found a genuine and significant effect: a 2.49 kg increase in strength (1RM) and a 0.30 kg increase in lean body mass.

Three hundred grams of muscle. That’s right, it’s been measured, and it’s a long way from what the packaging suggests. Two points to note from the same study: the effect diminishes with age, and it is more pronounced in people who are already fit — those who find it hardest to make progress are the ones who benefit most from supplementation.

The area where whey really comes into its own: speed

The benefits of whey are not just a marketing ploy. A 2009 study gave young men the same amount of essential amino acids in three forms — hydrolysed whey, casein or soya isolate — and measured muscle protein synthesis. Whey came out clearly on top:

Whey is digested quickly, is rich in leucine, and triggers a greater peak in muscle synthesis than other proteins. That much is accepted. The real question is whether this peak, measured over a few hours, actually translates into muscle mass after several months.

Where food catches up — and sometimes overtakes

As soon as you compare the powder to real food, the gap narrows. And in at least one case, it is reversed.

The study that everyone agrees on

In 2017, a research team conducted a 12-week study involving untrained young men divided into five groups: whey concentrate, hydrolysed whey, soya concentrate, leucine alone… and a placebo.

All groups gained the same amount: +2.2 kg of muscle mass, with comparable increases in the cross-sectional area of both type I and type II fibres. This included the placebo group. The authors explain why: everyone had increased their calorie intake and was already consuming 1.1 to 1.3 g of protein per kilogram per day. When the basic diet is adequate, the powder adds nothing at all.

But not all studies agree

It would be disingenuous to stop there. The study most favourable to whey is also the longest: 9 months of daily supplementation in untrained men and women, comparing whey, soya and carbohydrates.

So, one point for whey — but look at the ranges shown on the bars: they overlap considerably, which means that the results for different participants overlap. And note the key detail: the soya group, despite having the same protein intake of 1.4 g/kg/day, gained less lean body mass than the carbohydrate group. This result is difficult to explain by protein quality alone, and calls for caution before drawing a general conclusion from a single trial.

What about plant-based proteins?

This is the only area where the source really deserves your attention. A 2018 review explains why: plant-based proteins are, on average, less digestible and contain less leucine and fewer essential amino acids. For the same amount, they are less effective.

But ‘less effective at the same intake’ is not the same as ‘ineffective’. The 2021 meta-analysis, which compared animal and plant-based proteins in randomised trials, found no difference in absolute lean body mass or strength. The only advantage of animal protein was observed in the percentage of lean body mass among those under 50 (0.41 kg). And, crucially, the solution is well known: increase the intake or combine sources. A 2021 study confirmed this — 40 g of protein from a lysine-enriched plant-based blend stimulated muscle synthesis to the same extent as 40 g of chicken (0.046%/h versus 0.055%/h, a non-significant difference).

An important point to note: a 2018 pilot study found lower muscle mass in vegan men compared with vegetarians and omnivores, and a 2022 review warns of the risk of insufficient protein intake among elderly vegans. These studies do not compare diets with equal protein intake — they describe real-world diets, where total protein intake is often lower. It is the total intake that needs to be monitored.

So, how much protein should you have each day?

Since the overall figure takes precedence over the source, it is worth knowing the thresholds. A 2022 meta-analysis established these according to age:

For someone weighing 75 kg, that works out at around 120 g a day. You can easily get that from eggs, chicken, fish, dairy products and pulses — or with a protein shake on days when you can’t manage a proper meal.

In summary

So whey isn’t a magic product, but it isn’t a scam either: it’s a convenient, practical and inexpensive option per gram of protein, designed to bridge the gap between what you eat and what you should be eating. If that gap is zero, you can keep your money.

And if you’re wondering which supplements are really worth your money, we’ve ranked the best-researched ones for bulking: the best-researched supplements.

Every figure in this article is taken from the studies listed below, summarised on the basis of their abstracts alone. Several of these trials involved untrained or elderly participants, lasted between 8 weeks and 9 months, and the results are not all consistent — this is noted in the text. This is for information purposes only and is not a substitute for professional advice.